Add WebSocket ping/pong keep-alive mechanism

Implements RFC 6455 compliant ping/pong health checking to detect dead connections:
- Send ping frames every 10 seconds
- Monitor pong responses with 5-second timeout after each ping

desktop/tauri/src-tauri/Cargo.toml

@@ -42,6 +42,7 @@ tokio = { version = "1.44.2", features = ["macros"] }
 cached = "0.46.1"
 notify-rust = "4.10.0"
 assert_matches = "1.5.0"
+bytes = "1.5"
 tokio-websockets = { version = "0.5.0", features = ["client", "ring", "rand"] }
 sha = "1.0.3"
 http = "1.0.0"